This invention relates generally to the field of ship protection against mines, and more particularly to a novel and useful apparatus for protecting ships, that are not otherwise equipped with an on-board degaussing system, from magnetic influence mines during travel through known or suspected minefields.
Military ships are generally provided with on-board degaussing systems at the time they are built. Such on-board systems comprise electrical cables installed within the ship hull to form large coil loops and means for energizing the loops with electrical currents in a manner that will produce, as closely as possible, a magnetic field around the ship that will appear to magnetic influence mines as an undisturbed earth field. Examples of such on-board systems are found in U.S. Pat. Nos. 2,421,583; 12,730,063; 2,933,059; and 3,110,282.
During wartime or other national emergencies, it is often necessary to utilize merchant and other steel ships or vessels that were not designed or built with military service in mind, and so were not equipped with on-board degaussing system, for purposes which would expose them to the hazards of a minefield including magnetic mines. Such minefields are generally found in approaches to seaports and harbors rather than in the open sea.
Because the installation of on-board, permanently installed, degaussing systems on existing ships would be extremely expensive and would take such ships out of service for considerable periods of time and at a time when most needed, it would be of great benefit to have available a protective system that could be stored until needed and then used during the portions of a voyage where the dangers are most likely to exist.